There have been many proposals in recent years for passive type vehicle occupant restraint belt systems. Such proposals have been prompted by recognition that conventional systems in which the belt must be done up and undone by the occupant are often not used because the occupant finds it inconvenient to connect and disconnect the belt each time he or she enters or leaves the vehicle. The most common type of passive restraint belt system involves a movable belt transfer guide (either a guide ring or a movable anchor) located either inboard or outboard of the vehicle seat and movable back and forth in a manner to position the belt in a releasing or restraining configuration.
FIG. 1 of the accompanying drawings illustrates schematically an exemplary known passive belt system. A shoulder belt 10 leads from an emergency locking retractor 12 affixed to the vehicle floor inboard of the seat 14 outwardly through a belt guide 16 to an emergency release buckle 18 on a movable anchor 20. The anchor 20 slides along a guide rail 22 on the vehicle roof above the door 24 and is driven between a forward release position and a rearward restraint position by a drive device that comprises a gear-reduced reversible electric motor unit 26 that drives a drive wire 28. The wire is constrained to move along a predetermined path of fixed length by a sheath 30. Commonly, the drive wire is a so-called racked wire, an element that comprises a core wire and a helically wrapped tooth wire wound around the core wire. The output gear of the drive unit 26 drives the racked wire in opposite directions in response to energization of the motor by a circuit that includes a door switch for detecting opening and closing of the door 24. In this example of a passive belt system, the belt 10 is a shoulder belt which restrains the upper part of the vehicle occupant's body. The lower portion of the occupant's body is protected in the event of a collision or abrupt stop by an energy-absorbing knee bolster 32.
The restraint system shown in FIG. 1 is merely exemplary of a variety of two point and three point passive systems that have been proposed heretofore. Other systems having movable belt transfer guides on the door or adjacent the inboard side of the seat and driven by a drive device are known in the prior art.
One problem with many such systems involves the drive wire, such as a racked wire, for moving the belt guide member or a movable anchor. Such drive wires usually include a portion of a length slightly greater than the distance along which the movable belt guide ring or movable anchor moves between the restraining and releasing positions that extends like a tail out from the opposite side of the motor or other drive device from that portion leading from the motor to the guide ring or movable anchor. In FIG. 1 the portion just referred to is designated by the letter L and is guided within a sheath suitably installed within the side body panel adjacent the outboard side of the rear seat. The portion L and its equivalent in other restraint systems cause difficulties in the design and installation of the system. For one thing, the drive motor often has to be located at some distance from the belt transfer guide in order that the tail portion L of the wire can be located in a place in the vehicle body where there is room and where it does not interfere with other vehicle systems. This means that the length of drive wire is increased and the installation of the system becomes more complicated and costly. Moreover, the extra length of wire and sheathing increases costs, particularly with the use of relatively expensive racked wire material.